1. Field of the Invention
The present disclosure relates to a light emitting device.
2. Description of the Related Art
Conventionally, a light emitting device is known which is configured to emit white light by use of a light emitting element emitting blue light and a fluorescent material excited by absorbing a part or all of the blue light to emit light with longer-wavelength. In such light emitting device, it is demanded to uniform color tone of the white light emission and to improve light intensity of the white light emission.
For example, JP 2007-184326 A describes a thin light emitting diode lamp, wherein a blue light emitting diode chip is mounted on an inner bottom surface of a grooved concave portion provided on a top surface of a main body of the lamp, wherein a red photoconversion layer comprising red fluorescent material is provided to cover the diode chip, and wherein a green photoconversion layer comprising green fluorescent material is arranged such that blue light pass through the green photoconversion layer. In this thin light emitting diode lamp, the thickness of the red photoconversion layer at both right and left side surfaces extending across the grooved concave portion among the side surfaces of the blue light emitting diode chip is set to be thicker than the thickness of the red photoconversion layer at both right and left side surface extending in a longitudinal direction of the grooved concave portion among the side surfaces of the blue light emitting diode chip. Accordingly, the red photoconversion layer and the green photoconversion layer can uniform color tone of the white light emission in each place in this thin light emitting diode lamp. It further describes that light intensity of white light emission can be improved by providing a light transmission layer between the red photoconversion layer and the green photoconversion layer in this thin light emitting diode lamp, the light transmission layer comprising either of the red fluorescent material or the green fluorescent material, or comprising neither the red fluorescent material nor the green fluorescent material, or comprising a small amount of the red fluorescent material and/or the green fluorescent material.
JP 2007-184330 A describes a light emitting device configured such that blue light emitted from a blue light emitting diode chip transmits a red photoconversion layer comprising red fluorescent material, and then transmits a green photoconversion layer comprising green fluorescent material. It also describes that in this light emitting device, light intensity of white light emission can be improved by providing at the boundary of the red photoconversion layer and the green photoconversion layer a light transmission layer comprising either of the red fluorescent material or the green fluorescent material, or comprising neither the red fluorescent material nor the green fluorescent material, or comprising a small amount of the red fluorescent material and/or the green fluorescent material.